4 apostrophes in python code

Question

Reference https://github.com/noxrepo/pox/blob/carp/pox.py

I'm trying to understand what does the 4 apostrophes means? It doesn't look like commenting and near the end of the code there were another 3 apostrophes. Can someone help to explain the code below?

#!/bin/sh -

''''true
#export OPT="-u -O"
export OPT="-u"
export FLG=""
if [ "$(basename $0)" = "debug-pox.py" ]; then
  export OPT=""
  export FLG="--debug"
fi

if [ -x pypy/bin/pypy ]; then
  exec pypy/bin/pypy $OPT "$0" $FLG "$@"
fi

if type python2.7 > /dev/null 2> /dev/null; then
  exec python2.7 $OPT "$0" $FLG "$@"
fi
exec python $OPT "$0" $FLG "$@"
'''
from pox.boot import boot
if __name__ == '__main__':
  boot()

Answer 1

Overall Answer

The first three apostrophes start a multi-line string. The next apostrophe is just part of the contents of the string.

Inspecting the Result

The script stores the string in the __doc__ variable. After running the code interactively with python -i pox.py, it is easy to see the parsed docstring directly:

>>> print __doc__
'true
#export OPT="-u -O"
export OPT="-u"
export FLG=""
if [ "$(basename $0)" = "debug-pox.py" ]; then
  export OPT=""
  export FLG="--debug"
fi

if [ -x pypy/bin/pypy ]; then
  exec pypy/bin/pypy $OPT "$0" $FLG "$@"
fi

if type python2.7 > /dev/null 2> /dev/null; then
  exec python2.7 $OPT "$0" $FLG "$@"
fi
exec python $OPT "$0" $FLG "$@"

Note how the fourth apostrophe was kept as part of the docstring.

Details

According to the tokenize module, here is how Python views the above code:

NL        : '\n'
COMMENT   : '#!/bin/sh -'
NL        : '\n'
NL        : '\n'
STRING    : '\'\'\'\'true\n#export OPT="-u -O"\nexport OPT="-u"\nexport FLG=""\nif [ "$(basename $0)" = "debug-pox.py" ]; then\n  export OPT=""\n  export FLG="--debug"\nfi\n\nif [ -x pypy/bin/pypy ]; then\n  exec pypy/bin/pypy $OPT "$0" $FLG "$@"\nfi\n\nif type python2.7 > /dev/null 2> /dev/null; then\n  exec python2.7 $OPT "$0" $FLG "$@"\nfi\nexec python $OPT "$0" $FLG "$@"\n\'\'\''
NEWLINE   : '\n'
NAME      : 'from'
NAME      : 'pox'
OP        : '.'
NAME      : 'boot'
NAME      : 'import'
NAME      : 'boot'
NEWLINE   : '\n'
NAME      : 'if'
NAME      : '__name__'
OP        : '=='
STRING    : "'__main__'"
OP        : ':'
NEWLINE   : '\n'
INDENT    : '  '
NAME      : 'boot'
OP        : '('
OP        : ')'
NEWLINE   : '\n'
DEDENT    : ''
ENDMARKER : ''

Tokenization Script

Here is a Python 2.7 script that tokenizes the pox.py script:

from __future__ import print_function
import tokenize
import token

with open('pox.py') as f:
    for tok in tokenize.generate_tokens(f.readline):
        tok_type, tok_str, (srow, scol), (erow, ecol), logical_lineno = tok
        print('%-10s: %r' % (token.tok_name[tok_type], tok_str))